Mechanical seal device

ABSTRACT

A primary technical goal of the present invention is to provide a mechanical seal device in which a manufacturing cost of the parts is decreased, a satisfactory seal performance is exhibited even under severe operating conditions, and the device can be easily mounted outside relative to the housing. The mechanical seal device comprises a first diaphragm, a stationary seal ring, a rotary seal ring, a second diaphragm and a fluid passage which guides a sealed process fluid to the respective pressure receiving grooves of the first diaphragm and the second diaphragm wherein the first diaphragm retains a fixing section which is fixed relative to the mounting portion of a seal cover, a retaining section and a first pressure receiving face, the stationary seal ring retains a seal face which is retained by the retaining section, the rotary seal ring retains an opposing seal face which stays in a sealing contact with the seal face, and the second diaphragm is shaped and dimensioned in more or less an identical manner relative to the first diaphragm and retains a retaining section, a fixing section and a second pressure receiving face thereon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a mechanical seal device.More particularly, the invention relates to a mechanical seal devicedisposed at the end portion of a housing of large pumps, agitators orthe like which provides a seal against a sealed process fluid betweenthe housing and a rotary shaft whose pressure ranges from a low pressureto a high pressure.

2. Description of the Related Art

There has been a mechanical seal device for a high pressure pump as arelative art of the present invention, for example being disclosed inU.S. Pat. No. 5,114,163. However, this mechanical seal device is likelyto impose a higher cost for individual seal elements as they requirerelatively large dimensions. This is a first problem which needsimprovement. In addition, the seal device is so constructed that arotary seal ring and a stationary seal ring receive the pressure fromthe sealed process fluid in the same direction. Therefore, when thefluid pressure is increased, a high pressure is exerted in the samedirection to both the rotary seal ring and the stationary seal ring.Under this circumstance, if an excessive pressure is exerted by thesealed fluid against the rotary seal ring, there is a chance that therotary seal face departs from the mating stationary seal face, whichwill cause a breakage of a sealing contact. This is a second problem tobe solved. There remains another problem yet to be resolved. That is,the rotary seal ring is fixed relative to the rotary shaft while thestationary seal ring is fitted to the housing. Therefore, a thermalexpansion of the rotary shaft not only may hamper a sealing contactbetween the stationary seal face and the rotary seal face but also islikely to cause unwanted eccentricity.

FIG. 3 represents a mechanical seal device 200 as an example of theabove mentioned relative art, which will be described in details below.The mechanical seal 200 in FIG. 3 is formed and dimensioned in a largesize due to its deployment over a rotary shaft 148 which itself is largein diameter, which leads to a heavy weight of the entire seal assembly.Therefore, the mechanical seal device is typically divided into twosplit parts so that deployment of the seal device to the rotary shaft148 is simplified.

This split-type mechanical seal 200 provides a seal against the sealedprocess fluid between a housing 150 and the rotary shaft 148 at a pairof mating seal faces, i.e., a stationary seal face 161 of a stationaryseal ring 160 and a rotary seal face 171 of a rotary seal ring 170,whether the seal faces are subject to a relative sliding motion orremain stationary.

There is a clearance between an inner surface of the stationary sealring 160 and the rotary shaft 148 through which the sealed process fluidreaches a second gland 175 which is located closer to the rotary sealring 170.

A first gland 165 has a thick annular structure whose half cross sectionis shaped like an alphabet character L. An outer diameter surface of thestationary seal ring 160 is securely fitted with an inner diametersurface 167 of a cylindrically extending portion of the first gland 165.A flange section 166 which is disposed at the other end of thecylindrically extending portion of the first gland 165 makes a sealingcontact with the end surface of the housing 150.

The first gland 165 is fixed to the inner diameter surface of the splitstationary holder 168 which consists of two split pieces. The other endportion of the split stationary holder 168 is fixedly mounted on aprotruding portion which is located at one end of the housing 150.

The split stationary holder 168 fixedly retains the stationary seal ring160 with the first gland 165 being disposed therebetween. The stationaryseal ring 160 and the first gland 165 are retained within the splitstationary holder 168 and are fixated by means of clamping screw bolts153, 153.

As the first gland 165 covers the entire inner surface of the splitstationary holder 168, a flange section 166 of the gland between thestationary seal ring 160 and the housing 150 is made to have a thickwall so as to sustain a high pressure. Therefore, the first gland 165tends to be large in size and heavy in weight. In addition, a formingdie for the first gland 165 incurs a high manufacturing cost. These areproblems to be resolved.

The rotary seal ring 170 forms a loose fit relative to the rotary shaft148 with a clearance therebetween and the rotary seal face 171 makes asealing contact with the stationary seal face 161 for providing a fluidtight seal against the sealed fluid even under a relative slidingmovement. Outer diameter surface of the rotary seal ring 170 is fittedto an inner diameter surface 177 of the second gland 175. Also therotary seal ring 170 is securely fixed to the split rotary holder 178via the second gland 175. As this second gland 175 is large in diameter,a forming die for it results in a high manufacturing cost. Furthermore,different forms of the first gland 165 and the second gland 175necessitate use of different forming dies, which even further increasesthe total manufacturing cost. This is another problem yet to beaccommodated.

Split rotary holder 178 is fixed to the rotary shaft 148 by means of akey which does not appear in the figure. The split rotary holder 178 isassembled as an integral unit by fastening a couple of screw bolts 154,154 at a pair of mating surfaces. Therefore, the large-in-diametercylindrical portion of the second gland 175 provides a seal between therotary seal ring 170 and the inner surface of the split rotary holder178. Likewise, a small-in-diameter cylindrical portion of the secondgland 175 provides a seal between the rotary shaft 148 and the splitrotary holder 178. These two cylindrical portions both of which areshaped in a thick wall make it difficult to achieve a sensitive pressurecontrol at the mating faces even with the screw bolts being tightlyfastened, which is prone to a leakage of the sealed process fluid. Thispresents another problem to be remedied.

The second gland 175 thus formed makes the split rotary holder 178 heavyas well. Rotating the split rotary holder 178 with the rotary shaft 148tends to cause an eccentricity of the rotary shaft 148, and such aneccentricity in turn causes abrasions of the rotary seal face 171 of therotary seal ring 170 as well as of the stationary seal face 161 of thestationary seal ring 160. This imposes a further problem.

In a mechanical seal device thus constructed, the flange portion 166 ofthe first gland 165 located between the split stationary holder 168 andthe end face of the housing 150 is necessarily shaped in a thick wall soas to achieve a seal contact at the stationary seal face 161 and therotary seal face 171, and so is the radially extending portion of thesecond gland 175. This is another problem to be improved.

The stationary seal ring 160 is fixated relative to the housing 150 viathe split stationary holder 168 while the rotary seal ring 170 isfixedly secured to the rotary shaft 148 via the split rotary holder 178.If the rotary shaft 148 is subject to a thermal expansion in its outwardand axial direction, the seal contact between the stationary seal face161 and the rotary seal face 171 is disturbed. This creates anotherproblem to be solved.

The present invention is introduced to resolve the above mentionedproblems. A primary technical goal which this invention tries to achieveis to improve a seal performance of a mechanical seal device such that apair of seal faces which are mutually in contact are able to maintain afluid tight seal even under a great pressure or varying pressure of asealed process fluid.

Another goal is to fixate a rotary seal ring relative to a rotary shaftby integrating with a diaphragm in the outside of a housing such that agood seal performance is exhibited even under a great pressure orvarying pressure of a sealed process fluid or when the rotary shaft isbent.

Yet another goal is to decrease the manufacturing cost of parts involvedin the mechanical seal device, to simplify assembly of the parts, and toreduce the total manufacturing cost of the mechanical seal device as awhole.

SUMMARY OF THE INVENTION

A primary object of the present invention is to resolve the abovementioned technical problems, and a solution to such problems isembodied as follows.

A preferred embodiment of a mechanical seal device constructed inaccordance with the principles of the present invention is a mechanicalseal device to provide a seal against a sealed process fluid under avariable pressure ranging from a low pressure to a high pressure. Themechanical seal device comprises a seal cover being disposed at the endface of a housing and retaining a mounting face, a first diaphragm beingof an annular form and retaining a fixing section and a retainingsection, the fixing section being mounted on the mounting face of theseal cover, the retaining section being located on the opposite siderelative to the fixing section, a stationary seal ring being sealinglyretained by the retaining section of the first diaphragm and having aseal face at one end, a rotary seal ring having an opposing seal face,the opposing seal face being in a sealing contact relative to the sealface of the stationary seal ring, a second diaphragm being of an annularform and being shaped and dimensioned in more or less an identicalmanner relative to the first diaphragm and retaining a retaining sectionand a fixing section, the fixing section being connected with a rotaryshaft, a first pressure receiving groove being disposed between thefixing section and the retaining section of the first diaphragm, asecond pressure receiving groove being disposed between the fixingsection and the retaining section of the second diaphragm, and a fluidpassage guiding the sealed process fluid into the first pressurereceiving groove and the second pressure receiving groove.

In the mechanical seal device relative to the present invention, thefirst diaphragm and the second diaphragm which are shaped anddimensioned in more or less an identical manner relative to one anothercan be manufactured by using a common forming die. Therefore, there isno need of having two different forming dies which typically cost aboutfive to ten millions Japanese yen per piece, which decreases themanufacturing cost of the first diaphragm and the second diaphragm.

Also since the stationary seal ring and the rotary seal ring areresiliently supported, respectively, by the first diaphragm and thesecond diaphragm, the first diaphragm and the second diaphragm exhibitan elastic deformation according to the rotary shaft deformation causedby the following reasons; the rotary shaft becomes eccentric during itsrotation, a friction heat causes a thermal expansion of the rotaryshaft, or a shaft bending is caused by its self-weight. Even under anoccurrence of such an elastic deformation, the seal face of thestationary seal ring and the opposing seal face of the rotary seal ringretain a fluid tight sealing contact because the sealed process fluidacts on the first pressure receiving face and the second pressurereceiving face with an equal amount of pressure. Therefore, a sealperformance of the seal faces of the mechanical seal device can beensured.

The fluid pressure acting on the pressure receiving grooves of the firstdiaphragm and the second diaphragm wherein both diaphragms have anidentical form is applied to the grooves of an equal pressure receivingarea. Therefore, the stationary seal ring and the rotary seal ring areurged with approximately an equal amount of force by the sealed processfluid. The same amount of urging force by which the seal face of thestationary seal ring and the opposing seal face of the rotary seal ringare pressed against one another prevents an uneven wear of the sealfaces.

The first diaphragm resiliently supports the stationary seal ring whilethe second diaphragm resiliently supports the rotary seal ring whereinboth rings are urged against one another to achieve a sealing contact.Such a mechanical seal device has an easy assembly construction and caneasily be mounted on the outer part of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a mechanical seal device as a firstembodiment related to the present invention.

FIG. 2 is a cross sectional view of a pair of a first diaphragm and asecond diaphragm relative to the present invention which are arranged insymmetric positions.

FIG. 3 is a half cut-away sectional view of a mechanical seal device asa relative art of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Described below is the details of the figures of a preferred embodimentof a mechanical seal device constructed in accordance with theprinciples of the present invention. All the figures explained below areconstructed according to actual design drawings with accuratedimensional relations.

FIG. 1 depicts a cross sectional view of a mechanical seal device 1representing a first embodiment relative to the present invention.

In FIG. 1 and FIG. 2, 1 signifies a mechanical seal device. Thismechanical seal device 1 is intended to provide a seal on the outer partof a housing 60 of a pump or the like against a sealed process fluidwhich is located between the internal of the housing 60 and a rotaryshaft 50 being fitted within the housing 60.

End face of the housing 60 mounts a seal cover 20 which is securedtherein by means of screw bolts 37. The seal cover 20 retains an innerdiameter surface 20D to which a rotary shaft 50 loosely fits with aclearance being located therebetween. The seal cover 20 also has acylindrical mount section 20A which protrudes relative to the end faceof the cover. Mount surface 20B which is defined in the outer diametersurface of the mount section 20A disposes an engaging thread whichconsists of small continuous irregularities. The mount surface 20B ofthe engaging thread not only provides a sealing contact for avoiding aleakage of the sealed fluid when a first diaphragm 1 is fitted on butalso prevents the first diaphragm 10 thus fitted from coming off.

Inner diameter surface of the seal cover 20 retains an annular stepshoulder. An annular groove 20C is disposed between the step shoulderand a side plate 25 which is located beside the side wall of the sealcover 20 wherein the groove 20C is used to dispose a throttle valve 21.

Furthermore, a through hole is disposed in the annular groove 20Cwherein a pipe 40 is fitted to the through hole. Rubber-made, wheelshaped throttle valve 21 which is installed in the annular groove 20C isconnected with the pipe 40 so that a compressed fluid P can communicatebetween the two. The pipe 40 is located on the outer diameter surface ofthe seal cover 20 in a bisectional manner although three, four or fivemay be disposed in an equally spaced manner depending on designspecifications.

The throttle valve 21 retains an expansion chamber 21A therewithin, anda compressed fluid P fed through the pipe 40 induces the expansionchamber 21A to expand and, as a result, a throttle face 21B moves closerrelative to the diameter surface of the rotary shaft 50. Reducing thesealed process fluid by means of the expansion of the throttle face 21Blocated in the inner circumferential side of the throttle valve 21achieves to decrease a pressure exerted on the first diaphragm 10 and onthe second diaphragm 10 due to the sealed process fluid.

Upstream of the pipe 40 communicates a fluid compressor which is notshown in the figure, and a controller which is also omitted computes anappropriate valve action according to the correlation data obtained inadvance between the pressure of the sealed process fluid and otherfactors such as material strength of the rubber-made first diaphragm 10and the second diaphragm 10 and pressure receiving areas of a firstpressure receiving face 10A2 and a second pressure receiving face 10A1.The controller modulates a flow volume of the sealed fluid flowingwithin the inner surface of the throttle face 21B by means of a properaction of the throttle valve 21 thus computed accordingly. Modulation ofthe fluid pressure by the throttle valve 21 attains an optimized controlwith respect to an expansion ratio of the first diaphragm 10 and thesecond diaphragm 10 as well as a contact degree of a seal face 2Arelative to its mating seal face 12A.

FIG. 2 is referred to next. The first diaphragm 10 installed in themount section 20A of the seal cover 20 is molded by using a forming die.Material such as NBR, EPDM, CR, FVMQ, rubber-like resin or the like isused so that the first diaphragm 10 retains a first pressure receivingarea 10A2 for the sealed process fluid. In case that the circumferentialradius of the mold surface of the forming die becomes large, e.g., morethan several tens of centimeters, the first diaphragm 10 may be splitinto two semicircular halves for the purpose of a reduced cost of theforming die or an ease of assembly of the first diaphragm 10 relative tothe rotary shaft 50. The first diaphragm 10 consisting of the splithalves is shaped in a continuous ring form by means of a cure bondingapplied at the end surfaces of the split halves during the moldingprocess. Adoption of this type of forming die leads to a lowmanufacturing cost.

One end of the first diaphragm 10 defines a fixing section 10B whichengages the mount section 20A of the seal cover 20. The outer diametersurface of the fixing section 10B defines a fixing surface 10B1 which isfastened by a first hose band 8. Also the inner diameter surface of thefixing section 10B serves as a mount fixing face 10B2 (refer to FIG. 2).

As shown in FIG. 2, a retaining section 10D is disposed on the axiallyopposite side relative to the fixing section 10B. In addition, the innerdiameter surface of the retaining section 10D provides a stepped mountretaining face 10D2 for an easy installation of the stationary seal ring2. The outer diameter surface of the retaining section 10D serves as aretaining face 10D1 wherein the first hose band 8 is attached thereon.

A flexible section 10A is disposed between the fixing section 10B andthe retaining section 10D. The flexible section 10A bows towards itsouter diameter side, which allows the first diaphragm 10 to expand orcontract in the direction of the axis.

Furthermore, a pressure receiving groove 10C is disposed in the innerdiameter surface of the flexible section 10A, and the sealed processfluid acts on a first pressure receiving area 10A2 of the pressurereceiving groove 10C. Pressure of the sealed process fluid exerted onthe first pressure receiving area 10A2 forces the flexible section 10Ato elastically expand or contract in the direction of the axis, which inturn urges the stationary seal ring 2 to move toward the rotary sealring 12.

The fixing section 10B of the first diaphragm 10 is fixedly andsealingly fitted with the mount surface 20B by means of the engagingthread which consists of small continuous irregularities. Fastening ofthe first hose band 8 on the fixing surface 10B1 of the first diaphragm10 further improves the fixation of the fixing section 10B relative tothe mount surface 20B. The fixing surface 10B1 is fittingly sandwichedby a pair of bisected first covers 7, which then are secured byfastening screw bolts 36 from the both sides. The first cover 7 alsohangs over the outer diameter surface of the flexible section 10A of thefirst diaphragm 10.

Also the retaining section 10D of the first diaphragm 10 is fixed to theretaining surface 10D1 by fastening the first hose band 8. A bisectedfirst fastening band 3 is applied to the retaining surface 10D1 which isfixed by tightening screw bolts 36. The outer circumferential groove ofeach bisected first fastening band 3 integrally disposes a bisectedplate 4 therein.

For joining the plate 4 and the seal cover 20, 24 pieces of spiralsprings 6 are disposed in an equally spaced manner along thecircumference of the seal cover 2. The number of the spiral springs 6 isdetermined based on the desired contact force on the seal face 2A. Guidepins 5 for the spiral springs 6 are integrally disposed in the sealcover 20. These spiral springs 6 provide a resiliently urging force tothe stationary seal ring 2 via the first diaphragm 10. The resilientlyurging means using the spiral springs 6 for the stationary seal ring 2is disposed as a supplementary means according to a degree of expansionof the first diaphragm 10.

The stationary seal ring 2 is made of silicon carbide. One end of thestationary seal ring 2 serves as the seal face 2A. Also a clearance as afluid passage 15 is disposed between the inner diameter surface 2C ofthe stationary seal ring 2 and the rotary shaft 50. The inner diametersurface 2C of the stationary seal ring 2 has four lines of equallyspaced fixed grooves 2D therein. The number of the fixed grooves 2D isdetermined according to the design specifications. A joint face 2Blocated in the outer circumference of the stationary seal ring 2 isfittingly retained by the mount retaining surface 10D2 of the firstdiaphragm 10.

The engaging thread consisting of small continuous irregularities whichis formed on the joint face 2B of the stationary seal ring 2 ensures asealing fit between the joint face 2B and the mount retaining surface10D2. In addition, a clutch ring 22 integrally constructed with themount section 20A of the seal cover 20 disposes four clutches which areequally spaced at the circumferential end face of the clutch ring 22.These clutches engage the fixed grooves 2D of the stationary seal ring 2for preventing the stationary seal ring 2 from rotating.

The rotary seal ring 12 disposes an opposing seal face 12A on its endface. The opposing seal face 12A forms a sealing contact relative to theseal face 2A of the stationary seal ring 2. The rotary seal ring 12 hasdriving grooves 12D on its inner diameter surface 12C. These drivinggrooves 12D are disposed at four equally spaced locations along thecircumference. Also the outer diameter surface of the rotary seal ring12 disposes a joint face 12B. This joint face 12B fits the mountretaining face 10D2 of the second diaphragm 10. Mating of the joint face12B relative to the mount retaining face 10D2 can be achieved bypreparing screw thread on the both faces. Under this circumstance, bothof the mount retaining face 10D2 of the first diaphragm 10 and the jointface 2B of the stationary seal ring 2 are shaped in screw thread. Thatis, the mount retaining faces 10D2, 10D2 of the first diaphragm 10 andthe second diaphragm 10, respectively, are shaped and dimensioned in anidentical manner.

The mount fixing face 10B2 of the fixing section 10B of the seconddiaphragm 10 is fitted with a sleeve 11. The outer surface of the sleeve11 should be shaped and dimensioned in an identical manner relative tothe mount section 20A. That is, an engaging thread with the sameirregularities as those possessed in the mount section 20A should bedisposed in the mount surface 11B which is located on the outer diametersurface of the sleeve 11. Also a wall thickness of the sleeve 11 can bemade thin.

The sleeve 11 may be constructed as an integral piece of the mountfixing face 10B2 of the second diaphragm 10. In this case, an furtherend portion located outwardly relative to the fixing section 10B of thesleeve 11 is threaded and it mates with a tapped hole which is disposedin the inner diameter surface of a first clamp ring 30.

When the second diaphragm 10 is thus arranged, in order for the firstdiaphragm 10 and the second diaphragm 10 to have an identical form, themount fixing face 10B2 of the first diaphragm 10 should also deploy asleeve of the same form which is not shown in the figure. Then a matingtapped hole with the same diameter is fabricated in the inner diametersurface of the seal cover 20 (not shown in the figure), and the sealcover 20 and the sleeve 11 are screw fastened by mating the screw threadlocated at the end portion of the sleeve 11 relative to the tapped holeof the seal cover 20. In this case, it is noted that the seal cover 20has the tapped hole to mate with the sleeve 11 instead of the mountsection 20A.

The sleeve 11 is thus mounted on the rotary shaft 50. However, as thediameter of the rotary shaft 50 increases, an ease of manufacturing anda reduction in the machining cost of the sleeve 11 bear a greaterimportance. Also a simple assembly of the sleeve 11 onto the rotaryshaft 50 is another concern. For this reason, the sleeve 11 may be splitinto two pieces which are fitted to the rotary shaft 50 from its bothsides.

The method of disposing the sleeve 11 in the fixing section 10B of thesecond diaphragm 10 provides a merit that the second diaphragm 10 can bedisposed outside of the housing 60 instead of within the housing 60.Therefore, not only the construction of the mechanical seal device 1 issimplified, but also assembly of the mechanical seal device 1 is madeeasy. It also exhibits a good seal performance between the seal face 2Aand opposing seal face 12A.

The sleeve 11 is typically made of stainless steel, brass, cupper and soon.

The end portion of the sleeve 11 which fits the rotary shaft 50 disposesdriving pins 11A in a quadrisecting manner along the circumference.These driving pins 11A engage the driving grooves 12D of the rotary sealring 12 in order for both to rotate together.

The other end portion of the sleeve 11 locates an O-ring slot wherein anO-ring 13 is disposed. This O-ring 13 prevents the sealed process fluidfrom bleeding over the inner diameter surface of the sleeve 11 andleaking to an atmospheric region.

The second diaphragm 10 to retain the rotary seal ring 12 and a coupleof the second hose bands 8, 8 to fasten the both ends of the seconddiaphragm 10 are more or less identical in terms of the form and themounting method to the first diaphragm 10 and the first hose bands 8, 8for the first diaphragm 10, respectively. Also the second cover 7 hasthe same form as the first cover 7 and is disposed in a similar way. Thesecond diaphragm 10 and the second cover 7 are disposed in a mirrorsymmetrical locations relative to the first diaphragm 10 and the firstcover 7, respectively.

The second fastening band 3 wherein the plate 4 is taken out of thegroove therein also is shaped and dimensioned in an identical mannerrelative to the first fastening band 3.

The first diaphragm 10 to the left side of FIG. 2 and the seconddiaphragm 10 to the right side are manufactured by a single forming dieand arranged in mirror symmetrical locations. Therefore, adopting thesame form for the first diaphragm 10 and the second diaphragm 10significantly simplifies parts management after die forming. Also anaccidental swapping of the first diaphragm 10 and the second diaphragm10 does not cause a problem due to their identical form. Thiseffectively prevents incorrect part assembly from occurring in a machineusing the mechanical seal device 1.

As the first diaphragm 10 and the second diaphragm 10 have the identicalform, a first pressure receiving face 10A2 and a second pressurereceiving face 10A1 amount to have an equal pressure receiving area onwhich the sealed process fluid acts. As a result, the seal face 2A ofthe stationary seal ring 2 and the opposing seal face 12A of the rotaryseal ring 2 are urged against one another with the same face pressure,which prevents the contact force from being dislocated. Consequently,both of the seal face 2A and the opposing seal face 12A exhibit a betterseal performance and their durability is also improved.

The second diaphragm 10 has the same form as the first diaphragm 10being disposed in a mirror symmetrical locations, as shown in FIG. 2.Therefore, the first diaphragm 10 and the second diaphragm 10 can bemolded by a common forming die and arranged in symmetrical locations,which eases cost demands because two separate forming dies; one for thefirst diaphragm 10 and the other for the second diaphragm 10, are notneeded. As the forming die is very expensive (more than 5 millionsJapanese yen per piece), use of a common forming die makes a tremendouscontribution to the reduction of manufacturing cost of the firstdiaphragm 10 and the second diaphragm 10.

Also other peripheral parts associated with the first diaphragm 10 andthe second diaphragm 10, i.e., the first fastening band 3 and the secondfastening band 3, the first cover 7 and the second cover 7, the firsthose band 8 and the second hose band 8, can be shaped and dimensioned inan identical manner, respectively. This also significantly decreases themanufacturing cost of the parts. It further eases a burden of partsmanagement, especially in an assembly process of the parts.

A couple of clamp rings, a first clamp ring 30 and a second clamp ring31 which are located adjacent to the end portion of the sleeve 11 andthe second diaphragm 10, are fitted relative to the rotary shaft 50. Thefirst clamp ring 30 has a square cross section and an annular form. Thefirst clamp ring 30 either has a slit at one place of the circumferenceor is bisected and is fixed to the rotary shaft 50 by tightening thefastening screw bolts 35.

If the first clamp ring 30 does not have a bisected structure, then thering 30 is joined with the rotary shaft 50 by using an anchor bolt, notshown in the figure, whose tip is directly connected to the rotary shaft50. The second clamp ring 31 has an identical form with the first clampring 30 and disposes a flange section on its outer circumference. Thesecond clamp ring 31 is fixed relative to the rotary shaft 50 by meansof the fastening screw bolts 35.

The flange section of the second clamp ring 31 disposes a plurality ofbores therein which are located in an equally spaced manner along thecircumference. Screw rod 32 is inserted through the bore and the tip ofthe screw rod 32 is fixed relative to the seal cover 20. And the mountlocation of the second clamp ring 31 is adjusted with a nut whichengages the screw rod 32.

The first clamping ring 30 and the second clamping ring 31 enable it todispose the second diaphragm 10 and the sleeve 11 in a desirableposition.

This adjustment process is achieved by moving the second diaphragm 10 inthe axial direction by means of fastening the nut located in the screwrod 32 toward the first diaphragm 10. Next, the first clamping ring 30is fixed with the rotary shaft 60 by fastening the screw bolt 35disposed in the first clamp ring 30 after the optimal contact statebetween the seal face 2A and the opposing seal face 12A is recognized.Also the second clamp ring 31 is fixed with the rotary shaft 50 by asimilar method.

It is preferable that the second clamp ring 31, the screw rod 32 and theassociated nut are taken off after the completion of deployment of themechanical seal device 1.

In the mechanical seal device 1 thus constructed, there is a fluidpassage 15 between the inner diameter surface of the mechanical sealdevice 1 and the rotary shaft 50. The fluid passage 15 is defined by theinner diameter surface 20D of the seal cover 20, the inner surface ofthe first diaphragm 10, the inner diameter surface 2C of the stationaryseal ring 2, the inner diameter surface 12C of the stationary seal ring12, the inner surface of the second diaphragm 10 and the outer diametersurface of the rotary shaft 50. The sealed process fluid at a highpressure flows in from the housing 60 through the fluid passage 15 andacts on the first pressure receiving face 10A2 and the second pressurereceiving face 10A1 of the first diaphragm 10 and the second diaphragm10, respectively, which are made of rubber or resin material.

The fluid pressure acting on the first pressure receiving face 10A2 ofthe first diaphragm 10 and the second pressure receiving face 10A1 ofthe second diaphragm 10 wherein both of the receiving faces have anidentical form is applied to the faces of an equal pressure receivingarea. Therefore, the seal face 2A of the stationary seal ring 2supported by the first diaphragm 10 and the opposing seal face 12A ofthe rotary seal ring 12 supported by the second diaphragm 10 pressagainst one another with an equal amount of urging force whilemaintaining a fluid tight sealing contact.

The contact between the seal face 2A of the stationary seal ring 2 andthe opposing seal face 12A of the rotary seal ring 12 can be keptfluid-tight regardless of either possible bending of the rotary shaft 50due to its large diameter and large length or the axial expansion of theshaft due to the sliding frictional heat.

Proper adjustment of the throttle valve 21 for the sealed process fluidflowing through the fluid passage 15 can achieve an optimal contactsituation between the seal face 2A and the opposing seal face 12Awherein the pressure exerted on the first pressure receiving face 10A2of the first diaphragm 10 and the second pressure receiving face 10A1 ofthe second diaphragm 10 is regulated.

It is noted that the stationary seal ring 2 and the rotary seal ring 12are made of silicon carbide, carbon or ceramic material. Also the firstdiaphragm 10 and the second diaphragm 10 are made of rubber or resinmaterial. Material for the first diaphragm 10 and the second diaphragm10 is not limited to a rubber material as long as it retains rubber-likeelasticity such as resin materials. Form of the first diaphragm 10 andthe second diaphragm 10 should not be restricted to the aforementionedone. The first pressure receiving face 10A2 and the second pressurereceiving face 10A1 of an equal pressure receiving area whose crosssection is a semi-circle or U-shape can provide a similar performancewhen a couple of the annular bodies in the same form are arranged insymmetrical locations.

The mechanical seal device 1 of the present invention employs manycommon parts and the manufacturing cost of the parts can be decreasedaccordingly. Adopting such a construction wherein the stationary sealring 2 and the rotary seal ring 12 are retained by the first diaphragm10 and the second diaphragm 10, respectively, enables it to dispose themechanical seal device 1 in the outside relative to the end portion ofthe housing 60. Therefore, the mechanical seal device 1 in a large sizecan be disposed outside of the housing 60 for sealing on the rotaryshaft 50.

Different embodiments related to the present invention will be describednext.

A mechanical seal device 1 as a second embodiment related to the presentinvention disposes a fluid passage 15 within the inner diameter surface2C of a stationary seal ring 2 and the inner diameter surface 12C of arotary seal ring 12 and has joint faces 2B, 12B on the individual outerdiameter surfaces of the stationary seal ring 2 and the rotary seal ring12, respectively, against which the respective retaining section 10D,10D of a first diaphragm 10 and a second diaphragm 10 exhibit a sealingfit.

In the mechanical seal device 1 of the second embodiment, the firstdiaphragm 10 resiliently supports the stationary seal ring 2 while thesecond diaphragm 10 does the rotary seal ring 12, and the fluid passage15 of the sealed process fluid is defined within the inner diametersurfaces 2C, 12C of the stationary seal ring 2 and the rotary seal ring12, respectively. Under this construction, the respective pressurereceiving faces 10A2, 10A1 of the first diaphragm 10 and the seconddiaphragm 10 receive an even pressure from the sealed process fluid,which enables it to maintain a sealing contact between a seal face 2Aand an opposing seal face 12A. Also as the stationary seal ring 2 andthe rotary seal ring 12 are securely fitted relative to the resilientlydeformable retaining sections 10D, 10D of the first diaphragm 10 and thesecond diaphragm 10, respectively, the individual joint faces 2B, 12B ofthe stationary seal ring 2 and the rotary seal ring 12 are tightlysealed.

In a mechanical seal device 1 as a third embodiment related to thepresent invention, the annular body is divided in the direction of axiswherein the division faces are securely fastened as an integralconstruction, and the retaining section 10D of the first diaphragm 10fitted relative to the stationary seal ring 2 and the retaining section10D of the second diaphragm 10 fitted relative to the rotary seal ring12 are shaped in the form of cylindrical tube.

In the mechanical seal device 1 of the third embodiment, the stationaryseal ring 2 and the rotary seal ring 12 have split constructions suchthat the installation of the stationary seal ring 2 and the rotary sealring 12 onto the rotary shaft 50 is simplified. As the stationary sealring 2 and the rotary seal ring 12 are securely fitted to theresiliently deformable retaining sections 10D, 10D in a cylindrical formof the first diaphragm 10 and the second diaphragm 10, respectively, thestationary seal ring 2 and the rotary seal ring 12 can be easilyassembled to the rotary shaft 50 because of the split construction. Alsothe semicircular, split ring segments of the stationary seal ring 2 andthe rotary seal ring 12 can be easily manufactured by a compression moldforming wherein its forming die is fabricated at a low cost, whichdecreases a total manufacturing cost.

In a mechanical seal device 1 as a fourth embodiment related to thepresent invention, the throttle valve 21 is disposed in a upstreamregion of the fluid passage 15 of the sealed process fluid relative tothe first diaphragm 10.

In the mechanical seal device 1 of the fourth embodiment, as thethrottle valve 21 is located in the upstream side of the fluid passage15 relative to the first diaphragm 10 wherein the sealed process fluidflows in, when the pressure of the fluid becomes excessively high,actions of the throttle valve 21 ensure a sealing contact between thestationary seal ring 2 and the rotary seal ring 12 both of which havebisected constructions. More specifically, the throttle valve 21prevents the first diaphragm 10 and the second diaphragm 10 from beingsuffered from unwanted expansion and maintains a desired sealing contactbetween the seal face 2A of the stationary seal ring 2 and the opposingseal face 12A of the rotary seal ring 12 regardless of pressurefluctuations of the sealed fluid.

Disposition of the throttle valve 21 in the fluid passage 15 not onlydoes not require a mechanical seal device 1 to be disposed within thehousing 60 even in case of a high pressure sealed process fluid but alsomakes it possible to arrange the stationary seal ring 2 and the rotaryseal ring 12 outside the housing 60 wherein the seal rings are supportedby means of the first diaphragm 10 and the second diaphragm 10 alone.Also even in case of a bending situation due to a self-weight of therotary shaft 50 of a large size or a thermal expansion of the rotaryshaft 50, the use of the resiliently deformable first diaphragm 10 andthe second diaphragm 10 can provide a continuous sealing contact at theseal face 2A of the stationary seal ring 2 and the opposing seal face12A of the rotary seal ring 12.

A mechanical seal device 1 as a fifth embodiment related to the presentinvention retains a sleeve 11 which is fittingly inserted between thefixing section 10B of the second diaphragm 10 and the rotary shaft 50.

In the mechanical seal device 1 of the fifth embodiment, the sleeve 11is employed which is fitted with the fixing section 10B of the seconddiaphragm 10 and, at the same time, is securely fixed relative to therotary shaft 50. Therefore, the fixing section 10B of the seconddiaphragm 10 can be easily fixed relative to the rotary shaft 50. Alsoit simplifies the positioning process of the contact surface of theopposing seal face 12A of the rotary seal ring 12 relative to the sealface 2A. And it makes it easy to dispose the mechanical seal device 1outside the housing 60. In addition, the sleeve 11 can be of a thin-wallcylindrical structure which fits the rotary shaft 50. Therefore, thesleeve 11 tends to become a light weight. This avoids undesirableeccentricity of the rotary shaft during its rotation due to the weightof the sleeve 11, which in turn prevents a wear of the opposing sealface 12A relative to the seal face 2A due to the eccentricity.

Next will be described merits of a mechanical seal device 1 related tothe present invention from more technical points of view.

According to the mechanical seal device 1 of the present invention,adoption of a somewhat identical shape and dimension for the firstdiaphragm 10 and the second diaphragm 10 contributes the manufacturingcost reduction of the diaphragms wherein both the first diaphragm 10 andthe second diaphragm 10 can be fabricated by using a single commonforming die, hence a cost reduction in the forming die.

The stationary seal ring 2 and the rotary seal ring 12 are resilientlysupported by the first diaphragm 10 and the second diaphragm 10,respectively. Therefore, even when the rotary shaft 50 is eithersubjected to a thermal expansion due to the heat given by the sealedprocess fluid within the housing 60 or bent by the self weight of theprotruding portion of the shaft 50 which extends outward from thehousing 60, the first diaphragm 10 and the second diaphragm 10adaptively expand, according to the deformation of the rotary shaft 50,by the pressure of the sealed process fluid which acts on the firstpressure receiving face 10A2 and the second pressure receiving face10A1, respectively. As a result, the seal face 2A of the stationary sealring 2 and the opposing seal face 12A of the rotary seal ring 12 arekept in a sealing contact. This ensures a seal performance of themechanical seal device 1 by means of the sealing contact between theseal face 2A and the opposing seal face 12A.

The fluid pressure acting on the first pressure receiving face 10A2 ofthe first diaphragm 10 and the second pressure receiving face 10A1 ofthe second diaphragm 10 wherein both of the receiving faces have anidentical form is applied to the faces of an equal pressure receivingarea. Therefore, the seal face 2A of the stationary seal ring 2 and theopposing seal face 12A of the rotary seal ring 12 are urged withapproximately an equal amount of force by the sealed process fluid. Thesame amount of urging force by which the seal face 2A of the stationaryseal ring 2 and the opposing seal face 12A of the rotary seal ring 12are urged from one another enables it to exhibit a good sealperformance.

The first diaphragm 10 resiliently supports the stationary seal ring 2while the second diaphragm 10 resiliently supports the rotary seal ring12 wherein both rings are urged against one another to achieve a sealingcontact. Such a construction makes it easy to assemble these parts inthe outside of the housing 60 even if the rotary shaft 50 is large indiameter.

The split construction of the mechanical seal device 1 only requires tofit the split assemblies from the both sides. The throttle valve 21disposed in the fluid passage 15 allows the sealed process fluid to beadjusted for regulating a pressure applied to the first diaphragm 10 andthe second diaphragm 10. This not only achieves an optimal sealingcontact between the seal face 2A and the opposing seal face 12A, butalso prevents a friction wear between the seal face 2A and the opposingseal face 12A. Furthermore, as the fixing section 10B of the seconddiaphragm 10 is sealingly fixed relative to the rotary shaft 50 via thesleeve 11 which is fitted therebetween, the second diaphragm 10 can bedisposed outside of the housing 60. This not only simplifies theconstruction of the second diaphragm 10 but also makes it easy to mountthe assembly on the rotary shaft 50.

Having described specific embodiments of the invention however, thedescriptions of these embodiments do not cover the whole scope of thepresent invention nor do they limit the invention to the aspectsdisclosed herein, and therefore it is apparent that various changes ormodifications may be made from these embodiments. The technical scope ofthe invention is specified by the claims.

1. A mechanical seal device for providing a seal against a sealedprocess fluid, said mechanical seal device comprising: 1) a seal coverbeing disposed at the end face of a housing and retaining a mountingface; 2) a first diaphragm being of an annular form and retaining afixing section and a retaining section, said fixing section beingmounted on said mounting face of said seal cover, said retaining sectionbeing located on the other side relative to said fixing section; 3) astationary seal ring being sealingly retained by said retaining sectionof said first diaphragm and having a seal face at one end; 4) a rotaryseal ring having an opposing seal face, said opposing seal face being ina sealing contact relative to said seal face of said stationary sealring; 5) a second diaphragm being of an annular form and being shapedand dimensioned in more or less an identical manner relative to saidfirst diaphragm and retaining a retaining section and a fixing section,said fixing section being joined with a rotary shaft, 6) a firstpressure receiving groove defined by said fixing section and saidretaining section of said first diaphragm, and a clutch ring disposedbetween said first diaphragm and said rotary shaft, 7) a second pressurereceiving groove defined by said fixing section and said retainingsection of said second diaphragm, and a sleeve disposed between saidsecond diaphragm and said rotary shaft, and 8) a fluid passage guidingsaid sealed process fluid into said first pressure receiving groove andsaid second pressure receiving groove.
 2. A mechanical seal device asclaimed in claim 1 wherein said fluid passage communicates a passagelocated within the inner diameter surfaces of said stationary seal ringand said rotary seal ring.
 3. A mechanical seal device as claimed inclaim 1 wherein said stationary seal ring and said rotary seal ring areshaped in an annular form and divided along the axial direction, thedivision surfaces being fastened in an integral relation, and theretaining section of said first diaphragm to engage said stationary sealring and the retaining section of said second diaphragm to engage saidrotary seal ring are shaped in a cylindrical form.
 4. A mechanical sealdevice as claimed in claim 1 wherein a throttle valve is disposed in aupstream side of said fluid passage relative to said first diaphragm. 5.A mechanical seal device as claimed in claim 1 wherein a sleeve isfittingly disposed between said fixing section of said second diaphragmand the rotary shaft.
 6. A mechanical seal device as claimed in claim 1,wherein the first pressure groove axially expands by guiding the sealedprocess fluid therein, and wherein the seal face of the stationary sealring is pressed onto the opposing seal face of the rotary seal ring. 7.A mechanical seal device as claimed in claim 1, wherein the secondpressure groove axially expands by guiding the sealed process fluidtherein, and wherein the opposing seal face of the rotary seal ring ispressed onto the seal face of the stationary seal ring.
 8. A mechanicalseal device as claimed in claim 1, wherein the sealed process fluid actson a pressure receiving area of the first and second pressure receivinggrooves, wherein the first pressure groove axially expands by guidingthe sealed process fluid therein, and wherein the seal face of thestationary seal ring is pressed onto the opposing seal face of therotary seal ring, and wherein the second pressure groove axially expandsby guiding the sealed process fluid therein, and wherein the opposingseal face of the rotary seal ring is pressed onto the seal face of thestationary seal ring.
 9. A mechanical seal device as claimed in claim 8,wherein the seal face of the stationary seal ring supported by the firstdiaphragm and the opposing seal face of the rotary seal ring supportedby the second diaphragm press against each other with an equal amount ofurging force while maintaining fluid tight sealing contact therebetween.